There is known a method of removing scale by magnetic treatment water. For example, a report made under the title of “Substantiation experiments for preventing adhesion of marine organisms to the hull and the engine plant by magnetic treatment water” has been made so far in pp. 9 to 12 of “Collection of Papers of 50th Scientific Lecture Meeting of Tokyo University of Mercantile Marine published on Feb. 20, 2002 by Tokyo University of Mercantile Marine”.
According to the above-described report, a sea water magnetic treatment experiment uses a sea water magnetic treatment apparatus shown in FIG. 1. Specifically, an insulated electric wire 2 is wound around part of a pipe 1 as a treatment object using for sea water system by several turns to form a coil, and a weak electric current with a frequency ranging of from 5000 to 20000 Hz generated from a pulse generator 3 flows through the electric wire 2 to form a magnetic field that generates magnetic flux shown dashed lines in FIG. 1. In other words, the frequency of the weak electric current supplied to the electric wire 2 is swept in a range of from 5000 Hz to 20000 Hz.
According to the above-described report, water that flows through the pipe 1 in the direction shown by an arrow 4 is electrified, and the electrified water flows through the pipe 1 to prevent adhesion of scale, which marine organisms prefer to travel on, onto the inside surface of the pipe 1, and hence marine organisms can be prevented from adhering onto the local areas of the hull.
Moreover, as an apparatus using magnetic treatment water of the same kind, there is known an apparatus called “SCALE WATCHER” (registered trademark). This apparatus has an arrangement equivalent to that shown in FIG. 1 and an electric current that flows through the electric wire 2 is changed in a wide frequency extent ranging from 500 Hz to 3 kHz.
Of the above-described conventional technologies, the former report has described that while the frequency is being changed within the aforementioned frequency range, the electric current flows through the electric wire 2 to form the magnetic field to electrify water that flows through the pipe 1 and the thus electrified water flows through the pipe 1 to prevent adhesion of scale, which the marine organisms prefer to travel on, onto the inside surface of the pipe 1.
According to the description of the latter case, magnetic field energy and electric field energy (eddy current) generated by frequency-modulation are both used to progressively and physically change shapes and sizes of calcified calcium and minerals to decrease adhesion force of scale to thereby let scale flow from the inside of the pipe to the water.
In any case, although the basis for an argument is not yet established from a theory standpoint, according to the above-mentioned conventional apparatus, it was confirmed that the descaling effect is achieved when the electric current is flowing to the magnetic field generation coil wound around the pipe 1 while the predetermined frequency range is being searched for, and hence the above-mentioned conventional apparatuses do not intend to aim and remove specific scale.
Therefore, even if the above-mentioned conventional apparatuses are used for intending to aim and remove only specific scale, for example, since they do not intended to specify and remove only such specified scale, it is considered that the descaling effect should encounter with large energy loss. As a result, even if it is confirmed that the descaling effect is achieved through the above-mentioned conventional apparatuses, it is unavoidable that this descaling effect is achieved with plenty of time, and a problem arises, in which the above-mentioned descaling effect should not be efficient.
An object of this invention is to provide a descaling method and a descaling apparatus by which specific scale can be aimed and hence scales can be removed efficiently.